Multiple zone well completion method and apparatus

Abstract

The present invention discloses a system and method for completing a well for the collection of fluids from a plurality of subterranean zones at different depths. The system includes a fluid pathway along which a first and second fluid travel. The first and second fluids form an interface that is moved along the fluid pathway to cause the formation of a fracture in the zones. The pressure at any point along the fluid pathway depends upon the position of the interface.

What is claimed is: 
     
       1. A method for completing a well for the collection of fluids from a plurality of subterranean zones at different depths, the well having a wellbore extending from an accessible upper end through the plurality of zones with a conduit positioned in the wellbore to define a fluid pathway including the conduit and an area between the conduit and the wellbore, comprising the steps of: introducing a first fluid having a first density into the fluid pathway;   introducing a second fluid having a second density different from the first density into the fluid pathway, wherein the first and second fluids produce within the wellbore a first fluid pressure on a first zone adjacent to an interface between the first and second fluids with the first fluid pressure being sufficient to form a fracture in the first zone; and   changing the position of the interface to a location along the fluid pathway adjacent to a second zone to produce a second fluid pressure on the second zone with the second fluid pressure being sufficient to form a fracture in the second zone.   
     
     
       2. The method, as claimed in claim 1, further comprising: sediments containing the plurality of subterranean zones; and wherein:   the first fluid has a pressure gradient along the fluid pathway that is greater than the fracture extension pressure gradient of the sediments to be fractured.   
     
     
       3. The method, as claimed in claim 1, wherein: the first fluid comprises clay and a bivalent or trivalent cation to dehydrate the clay.   
     
     
       4. The method, as claimed in claim 1, further comprising: sediments containing the plurality of subterranean zones; and wherein:   the second fluid has a pressure gradient along the fluid pathway that is less than the fracture extension pressure gradient of the sediments to be fractured.   
     
     
       5. The method, as claimed in claim 1, wherein: when the interface is positioned adjacent to the second zone, the fluid pressure on the first zone is less than the first fluid pressure.   
     
     
       6. The method, as claimed in claim 1, wherein: when the interface is positioned adjacent to the second zone, the second fluid exerts a fluid pressure on the first zone that is insufficient to fracture the first zone.   
     
     
       7. The method, as claimed in claim 1, wherein the changing step comprises: injecting the first fluid into the fluid pathway at a first rate; and   injecting the second fluid into the fluid pathway at a second rate, wherein the first rate and second rate depend upon the desired position of the interface.   
     
     
       8. The method, as claimed in claim 7, wherein the changing step comprises: injecting the first fluid into the area between the conduit and the wellbore; and   injecting the second fluid into the conduit.   
     
     
       9. The method, as claimed in claim 1, wherein the changing step comprises: monitoring the fluid pressure at a plurality of points in the fluid pathway to determine the position of the interface.   
     
     
       10. The method, as claimed in claim 1, wherein the changing step comprises: first moving the interface from the first zone to the second zone: and   second moving the interface from the second zone to the first zone, wherein the first zone is at a greater depth than the second zone.   
     
     
       11. The method, as claimed in claim 1, wherein the first fluid comprises solid particles having a median size and further comprising: third introducing into the fluid pathway a third fluid having a density different from the first and second fluid densities, the third fluid comprising a third proppant having a third proppant median size greater than the solid particles median size.   
     
     
       12. The method, as claimed in claim 1, wherein the first fluid comprises solid particles having a median size ranging from about 300 to about 400 mesh (Tyler) and further comprising: third introducing into the fluid pathway a third fluid having a third density different from the first and second densities, the third fluid comprising a third proppant having a median size ranging from about 40 to about 60 mesh (Tyler).   
     
     
       13. The method, as claimed in claim 12, further comprising: fourth introducing into the fluid pathway a fourth fluid having a fourth density different from the first, second, and third densities, the fourth fluid comprising a fourth proppant having a fourth proppant median size ranging from about 12 to about 20 mesh (Tyler).   
     
     
       14. A system for fracturing a plurality of subterranean zones, comprising: a wellbore extending from an accessible upper end into the zones to be fractured;   a conduit located within the wellbore, the conduit extending from the earth's surface to a location below the deepest zone to be fractured and communicating with an area between the wellbore and the conduit at a location at or below the deepest zone to be fractured to define a fluid pathway including the conduit and the area between the conduit and the wellbore, the fluid pathway contacting the portion of the zone to be fractured;   a first fluid positioned along the fluid pathway in the wellbore; and   a second fluid positioned along the fluid pathway in the wellbore, the second fluid having a different density than the first fluid and forming an interface with the first fluid, wherein the fluid pressure exerted on the zones to be fractured is varied by altering the position of the interface along the fluid pathway.   
     
     
       15. The system, as claimed in claim 14, wherein: the conduit is sealed from the area between the conduit and the wellbore above the deepest zone to be fractured.   
     
     
       16. The system, as claimed in claim 14, wherein: the conduit comprises pipe having an outer diameter smaller than the diameter of the wellbore.   
     
     
       17. The system, as claimed in claim 14, wherein: the conduit is detached from the wellbore.   
     
     
       18. The system, as claimed in claim 14, wherein the first fluid comprises solid particles having a median size and further comprising: a porous surface at the bottom end of the conduit and in communication with the conduit, the porous surface having a pore size less than the median size of the solid particles.   
     
     
       19. The system, as claimed in claim 14, further comprising: a container located below the conduit for collecting objects in the first and second fluids.   
     
     
       20. A method for completing a well for the production of fluids from sediments, the well having a wellbore extending from an accessible upper end into the formation with a conduit positioned within the wellbore to define a fluid pathway including the conduit and an area between the conduit and the wellbore, comprising the steps of: introducing a first fluid and a second fluid of different densities into the wellbore, wherein the first fluid has a pressure gradient along the fluid pathway greater than the fracture extension pressure gradient of the sediments to be fractured; and   positioning an interface between the first and second fluids adjacent to the sediments to be fractured to produce a sufficient fluid pressure on the sediments to form a fracture in the sediments.   
     
     
       21. The method, as claimed in claim 20, wherein: the first fluid comprises a proppant having a median size ranging from about 300 to about 400 mesh (Tyler).   
     
     
       22. The method, as claimed in claim 20, wherein: the second fluid has a pressure gradient along the fluid pathway that is less than the fracture extension pressure gradient of the sediments to be fractured.   
     
     
       23. The method, as claimed in claim 20, wherein the formation comprises a plurality of zones and the positioning step comprises: first positioning the interface adjacent to a first zone in the sediments to produce a sufficient fluid pressure on the first zone to form a fracture in the first zone; and   second positioning the interface adjacent to a second zone in the sediments to produce a sufficient fluid pressure on the second zone to form a fracture in the second zone.   
     
     
       24. The method, as claimed in claim 20, wherein: the fluid pressure on the sediments depends upon the position of the interface along the fluid pathway.   
     
     
       25. The method, as claimed in claim 20, wherein the positioning step comprises: first positioning the interface adjacent to the sediments to be fractured to form a fracture in the sediments with the first fluid flowing into the fracture at a first rate; and   second positioning the interface at a distance from the sediments to be fractured with the first fluid flowing into the fracture at a second rate, wherein the first rate of flow is greater than the second rate of flow.